1. Field of the Invention
The present invention relates to a graphic image display apparatus and, more particularly, a graphic image display apparatus suitably used in game machines adapted to carrying out a high speed up/down and/or right/left inversion of a specific graphic image and displaying the inverted image.
2. Description of the Related Art
Recently, as game machines adapted to highly sophisticated games are developed, graphic image display apparatuses of the type under consideration are required to have various special functions for effective presentation of images to players. Such special functions may include the function of laterally inverting (right/left inversion) the image of a character of the game and displaying it with the original image of the character simultaneously on the screen.
In a first prior art graphic image display apparatus, data for a graphic to be displayed and data for an inverted graphic thereof on a graphic read-only memory (ROM) are mapped as independent sets of data. This will be explained later in detail. As a result, the volume of data to be stored in the graphic ROM increases proportionally relative to the desired number of inverted graphics which consequently requires a large circuit. In addition, as the storage capacity of the graphic ROM increases, the power consumption of the graphic image display apparatus also increases.
In a second prior art graphic image display apparatus (see JP-A-62-192793), graphic data for display is temporarily stored in a shift register, a normal graphic display and a right/left inverted graphic display are carried out by storing them in a line buffer in a descending order or in an ascending order.
In the second prior art graphic image display apparatus, however, since the original graphic can be inverted only right/left, it is impossible to invert or replace selected dots in the original graphic nor is it possible to display only selected dots of the original graphic.